title: L-Proline uptake in Saccharomyces cerevisiae mitochondria can contribute to bioenergetics during nutrient stress as alternative mitochondrial fuel.
abstract: L-Proline (pyrrolidine-2-carboxylic acid) is a distinctive metabolite both biochemically and biotechnologically and is currently recognized to have a cardinal role in gene expression and cellular signaling pathways in stress response. Proline-fueled mitochondrial metabolism involves the oxidative conversion of L-Proline to L-Glutamate in two enzymatic steps by means of Put1p and Put2p that help Saccharomyces cerevisiae to respond to changes in the nutritional environment by initiating the breakdown of L-Proline as a source for nitrogen, carbon, and energy. Compartmentalization of L-Proline catabolic pathway implies that extensive L-Proline transport must take place between the cytosol where its biogenesis via Pro1p, Pro2p, Pro3p occurs and mitochondria. L-Proline uptake in S. cerevisiae purified and active mitochondria was investigated by swelling experiments, oxygen uptake and fluorimetric measurement of a membrane potential generation (ΔΨ). Our results strongly suggest that L-Proline uptake occurs via a carried-mediated process as demonstrated by saturation kinetics and experiments with N-ethylmaleimide, a pharmacological compound that is a cysteine-modifying reagent in hydrophobic protein domains and that inhibited mitochondrial transport. Plasticity of S. cerevisiae cell biochemistry according to background fluctuations is an important factor of adaptation to stress. Thus L-Proline → Glutamate route feeds Krebs cycle providing energy and anaplerotic carbon for yeast survival.
authors.affiliation: Department of Medicine and Health Sciences, University of Molise, 86100, Campobasso, Italy, pallotta@unimol.it.
authors.forename: Maria Luigia
authors.initials: ML
authors.lastname: Pallotta
mesh_terms: D002244:Carbon / Q000378:metabolism; D004734:Energy Metabolism; D005502:Food; D018698:Glutamic Acid / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D011392:Proline / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D018698:Glutamic Acid; D002244:Carbon; D011392:Proline; D009584:Nitrogen